Introduction: Delirium is a frequent and important problem in the intensive care unit (ICU), and non-pharmacological means of prevention are limited. The importance of the physical environment in the occurrence of delirium in intensive care has been reported, particularly the presence of windows and daylight. We organized a trial to evaluate if the installation of virtual windows in the form of paintings in rooms without an actual window can limit the occurrence of delirium in ICU patients. Methods: We conducted a retrospective pre and post cohort study in a surgical ICU of a university-affiliated hospital. Patients residing for more than 48 hours in a windowless room before and after the installation of virtual windows were included in the trial. The primary endpoint was the incidence of a positive screening test for delirium during their time in the ICU. The Intensive Care Delirium Screening Checklist (ICDSC) was used as an objective screening tool to assess the occurrence of delirium. Results: A total of 400 patients were included in this trial (pre group: n = 200; post group: n = 200). The groups were well balanced except for the score APACHE II who was significantly higher in the post intervention group. The incidence of a positive screening test for delirium was similar in both groups after correction for confounding factors (29% vs 27%; OR 0,906 [0,584-1,402], p=0,656). Conclusion: The installation of virtual windows did not reduce the incidence of delirium in a surgical intensive care unit. Keywords Critical care, delirium, windows, prevention, circadian cycle.